The present invention relates generally to radio transceivers and, more particularly, to a radiotelephone, and associated method, operable in a cellular communication system which includes interface apparatus which facilitates usage of the radiotelephone by a user while the user performs additional tasks, such as operating a motor vehicle.
A communication system is comprised, at a minimum, of a transmitter and a receiver interconnected by a communication channel. A radio communication system comprises one type of communication system wherein the communication channel interconnecting the transmitter and the receiver is formed of a radio frequency channel. No fixed connection is required between the transmitter and receiver of a radio communication system. Therefore, a radio communication system is advantageously utilized when a fixed connection between the transmitter and the receiver would be inconvenient or impractical.
A cellular communication system is one type of radio communication system. In a cellular communication system, numerous fixed-site transceivers, referred to as "base stations," are installed at spaced-apart locations throughout a geographical area. Each of the base stations contains circuitry to receive modulated signals transmitted thereto, and to transmit modulated signals therefrom. A radiotelephone transmits the modulated signals to a base station, and a base station transmits the modulated signals to the radiotelephone. The modulated signals are transmitted upon selected frequency channels allocated for such cellular communications.
A plurality of radiotelephones may be operated simultaneously when the modulated signals transmitted by the different radiotelephones are transmitted upon dissimilar channels. The dissimilar channels may be defined, e.g., to be of dissimilar frequencies or to be of dissimilar transmission the periods upon a single range of frequencies. (The modulated signals transmitted by base stations to the radiotelephone are similarly transmitted upon dissimilar channels.) As the power levels of the modulated signals generated by both the radiotelephones and the base stations are relatively low, the same frequency channel may be reused throughout a geographical area to transmit the modulated signals between a radiotelephone and a base station. In such manner, a cellular communication system efficiently utilizes the channels of the frequency band allocated for such use.
Technological improvements have decreased the cost associated with communication in a cellular communication system. As a result, ever-increasing numbers of users are able to made use of a cellular communication system to communicate thereupon. Of particular popularity is the use of a radiotelephone to communicate in a cellular communication system when the user is traveling in an automotive vehicle. Radiotelephones constructed for installation within an automotive vehicle are conventionally referred to as mobile phones. As no fixed connection is required between the radiotelephone and a base station, communication is permitted therebetween as long as the vehicle in which the radiotelephone is positioned is within the geographical area encompassed by the cellular communication system.
The steps required to be taken to effectuate a communication link between a radiotelephone, such as a mobile phone, and a base station are quite similar to the steps required to be taken to effectuate communication when utilizing a telephone of a conventional, wireline, telephonic system. Namely, a telephone number is entered by a user by way of a telephonic keypad. An additional key is also actuated to cause transmission of the telephone number to the base station. The telephone number is associated with a particular telephone situated at a remote location, and, once the telephone number is transmitted by the radiotelephone to a base station, effectuation of a communication link with the telephone situated at the remote location is accomplished in conventional manner.
Quite frequently, when the radiotelephone is positioned in an automotive vehicle, the user of the phone is also the operator of the vehicle. When operating the vehicle, primary attention must be directed to that task. Only minimal attention may be allocated to taking the steps required to effectuate communication in a cellular communication system. Although the required step of entering a telephone number is not, of itself, a complex task, visual inspection of the telephonic keypad is typically required of the user to ensure correct dialing of the telephone number. This visual inspection required to dial the telephone number detracts from the attention which must be directed to operating the automotive vehicle.
To minimize the visual inspection required to enter the telephone number, therefore, mobile phone constructions frequently include features to simplify the task of effectuating a communication link with a base station. For instance, the speaker and microphone, conventionally mounted upon a telephonic handset, are, in some mobile phone constructions, also fixedly mounted within the vehicular compartment of the automotive vehicle. Rather than holding a telephonic handset to position the speaker and microphone proximate to the user, the user may speak towards the microphone mounted in the fixed position in the vehicular compartment and listen to signals generated by the speaker similarly mounted in fixed position therein. Such feature is frequently referred to as a "hands-free" feature permitting "hands-free" operation of the mobile phone.
Additionally, existing mobile phone constructions frequently include features to reduce the number of steps necessary to dial a telephone number. Analogous to conventional, wireline telephonic constructions permitting "speed-dialing," mobile phone constructions include features permitting such dialing of a telephone number. Conventionally, a switch is associated with a single telephone number, and, when the switch is actuated, the telephone number associated therewith is dialed. When appropriately positioned in the vehicular compartment of the automotive vehicle, the operator of the automotive vehicle, upon memorizing the location of the switch, can dial the telephone number associated therewith by actuation of the switch.
However, as the switch is associated with a single telephone number (i.e., there is a one-to-one correspondence between the switch and the telephone number), an increase in the number of telephone numbers which may be "speed-dialed" requires a corresponding increase in the number of switches. The location of each switch must be memorized to avoid the requirement of a user to inspect visually the location of the switch prior to actuation thereof. With each additional switch, the likelihood that the user, either as an impulse or as of necessity, must visually inspect the location of the switch prior to actuation thereof increases, as the user must both memorize the locations of the switches and the telephone numbers associated therewith to actuate a switch without first making a visual inspection of the location thereof. As the attention of the operator of an automotive vehicle must be directed primarily to the operation of a vehicle, such a need or impulse to locate visually a switch prior to actuation thereof detracts from the operator's attention which should otherwise be directed towards operation of the automotive vehicle.
What is needed, therefore, is an improved radiotelephone, and interface apparatus therefor, which facilitates usage of the radiotelephone by a user.